In order to remove an initial failure, screening is performed on a semiconductor device such as a semiconductor integrated circuit. As currently used screening methods, a method utilizing voltage acceleration and a method utilizing temperature acceleration are cited as typical ones. Generally, if a semiconductor device is used at a room temperature (25° C. to 30° C.), an initial failure is generated during a period of time from the start of its use to almost 1000 hours, and an actual lifetime of the semiconductor device expires after about three hundred thousand hours.
Accordingly, if the screening of the semiconductor device is performed at a room temperature, a long period of time such as almost 1000 hours has to be spent for the screening. Therefore, generally, the screening is normally performed at 125° C. for about 1 to about 96 hours, not for 1000 hours.
A personal computer or a server using semiconductor devices having large heating amounts has a large-sized fin provided on a substrate for restraining a rise in temperatures of the semiconductor devices and for cooling the semiconductor devices, and performs fan cooling, liquid cooling, gas cooling, Peltier cooling and the like. When the screening of the semiconductor devices having large heating amounts is performed, a difference in the heating amounts among each of semiconductor devices is generated due to a manufacturing variation and the like, even under the same voltage and temperature. Depending on the difference in the heating amounts, the temperatures of the semiconductor devices are sometimes out of the regulated temperature control range.
In a conventional testing device that performs the screening, a thermal head having a heater is provided for each of semiconductor devices. When the screening of the semiconductor devices is performed, a solution (water, Fluorinert, or the like) whose temperature may be varied is made to circulate through the thermal heads, and the corresponding thermal heads are placed in contact with all the semiconductor devices, to thereby conduct temperature control of the semiconductor devices through the heat of the solution and the heaters.
Concretely, among semiconductor devices mounted on the testing device, one having the largest heating amount is specified, and a temperature of the solution circulated through the thermal head is set so that a heater power with which the temperature of the semiconductor device reaches a regulated temperature becomes minimum. Specifically, the temperature of the solution is set based on the semiconductor device having the largest heating amount. The other semiconductor devices are controlled so that temperatures thereof reach the regulated temperature, by individually adjusting the heater power.
However, when the variation in the heating amounts among semiconductor devices mounted on the testing device is significantly large, the temperatures of the semiconductor devices are sometimes deviated from a range of the regulated temperature when performing the screening. For instance, if there exists a semiconductor device having a large heating amount whose temperature cannot be controlled to fall within the regulated temperature unless the heater power is set to almost 0% and the temperature of the circulated solution is set to approximately room temperature, the temperature of the semiconductor device having a small heating amount sometimes does not reach the regulated temperature as depicted in FIG. 17, since the generated heat of the semiconductor device is drawn due to the low temperature of the solution, regardless of the heater power which is set to almost 100%.
FIG. 17 is a view for explaining an example of the temperature control of the semiconductor devices when performing the screening. In FIG. 17, a vertical axis represents temperature and a horizontal axis represents time. Further, TR corresponds to a regulated temperature (typical value) when performing the screening, and TRU and TRL correspond to an upper limit value and a lower limit value of the regulated temperature, respectively. As an example, the temperature of the semiconductor device having a large heating amount and the temperature of the semiconductor device having a small heating amount among the semiconductor devices mounted on the testing device are respectively represented by DV11 and DV12.
As depicted in FIG. 17, if the temperature of the circulated solution is lowered so that the temperature of the semiconductor device having a large heating amount (DV11) falls within a range of the regulated temperature, the temperature of the semiconductor device having a small heating amount (DV12) sometimes cannot reach the lower limit value TRL of the regulated temperature because of the insufficient heating amount even when the heater power is set to maximum.
Such a semiconductor device whose temperature is out of the regulated temperature (whose temperature does not reach the regulated temperature within a given set time) is the one to which a regulated stress with which the initial failure is exhibited is not applied, so that the screening has been performed again by cutting off a power supply supplied to the semiconductor device, or the semiconductor device has been handled as a defective product.
Further, various temperature control techniques for performing tests of semiconductor devices have been proposed in Japanese Laid-open Patent Publication No. 2005-265665, Japanese Laid-open Patent Publication No. 2001-51012, Japanese Laid-open Patent Publication No. 2006-310631, Japanese Laid-open Patent Publication No. 2000-304804 and Japanese Laid-open Patent Publication No. 2005-156172.
Japanese Laid-open Patent Publication No. 2005-265665 proposes a burn-in device that makes a heating block for heating an electronic component under test and a cooling block for cooling the electronic component under test in a thermally floating state, and enables to individually control temperatures of electronic components, to thereby simultaneously perform a burn-in test on the large number of electronic components having different self-heating amounts.
Japanese Laid-open Patent Publication No. 2001-51012 proposes a semiconductor testing system that enables to maintain a temperature of an IC device at a certain temperature by controlling a temperature of a contact block in which the IC device is housed. Concretely, there is proposed a temperature control technique in which a hollow portion is provided in the contact block in which the IC device is housed, and a high-temperature control liquid or a low-temperature control liquid is selectively jetted, in accordance with a base temperature of the IC device, to the contact block from a high-temperature control nozzle or a low-temperature control nozzle provided in the hollow portion.
Japanese Laid-open Patent Publication No. 2006-310631 proposes a temperature control technique with which a temperature of a target such as an electronic component can be controlled in an accurate and quick manner by enabling to quickly perform heating processing or cooling processing on the target.
Japanese Laid-open Patent Publication No. 2000-304804 proposes a burn-in device with which temperatures of devices to be measured may be individually controlled and an improvement in temperature accuracy and operability in a burn-in test may be realized.
Japanese Laid-open Patent Publication No. 2005-156172 proposes a test burn-in device that measures and adjusts a temperature of a semiconductor element such as a middle-power and a high-power IC in an element unit, and performs, at the same time, burn-in to exclude a defective product having an initial failure.